This invention relates to methods and apparatus for use in the baiting of fish and crustacea. It is particularly concerned with delayed release bait canisters for use with lobster, crayfish and crab pots, but the canister disclosed herein can also be used in fishing for finned fish. The invention is also concerned with delayed release devices suitable for use with such methods and canisters.
As a matter of convenience, this invention will be described with reference to cray and crab fishing using traps commonly known as pots, though it is not limited thereto.
The present invention is based upon the appreciation that some fishermen prefer to use large pieces of fresh bait in when trapping crays and crabs, while others prefer to employ dried or processed bait pellets which act as attractants rather than food but which tend to break-up quickly in water. Even large pieces of bait have a short life in a cray pot because they are quickly consumed or broken up by small fish, under-size crabs and crays and, particularly, by arthropods such as sea lice. Many professional cray-fishermen consider that crays are more likely to venture out to explore pots at certain times of the day or at certain tides, so they try to drop their pots accordingly but, as it may take hours to drop a line of pots, only a few can be placed on time. It would be ideal for such fishermen to have a bait canister that (i) is well-suited for use with cray and crab pots, (ii) released bait odours as soon as the pot is dropped, (iii) excluded access to the bait by sea lice, (iv), released large pieces of fresh bait within the trap at a time determined by the fishermen, and (iv), did not require cleaning out after use.
U.S. Pat. No. 4,914,856 to Kennedy et al discloses a bait container for use with crustacean traps which is formed from plastic tubing fitted with end-caps. The wall of the tubing is slotted wall to form a grill to prevent the loss of large pieces of bait, and a hinged door is provided to allow the bait to be introduced into the container. The purpose of this container is to prevent the bait from being removed by crays or crabs while allowing bait odours to escape and attract the desired crustacea, but the grill slots are large enough to allow sea lice to enter but generally too small to permit the container to be self-cleaning, and, delayed release is not possible. Russian patent 2,064,258 to Sologub discloses the use of a plastic bait container having fine perforations and removable end caps but, in this case, the perforations are tightly sealed with a rubber flap that is held in place using a corrodible link to effect timed release. The intention is apparently to delay the release of bait odours and prevent any access to the bait by crays and crabs. Not only do the applicants consider these objectives to be misguided, but such containers will be difficult and unpleasant to clean.
U.S. Pat. No. 3,654,725 to Kingston discloses the use of bait pouches containing preserved and pre-packaged bait but, here, the pouch is slit open with a draw-knife after a predetermined time. The knife is spring-loaded and is released by the use of a corrodible link. The mechanism is large and expensive and unsuited for placing in craypots. U.S. Pat. No. 3,842,529 to Richard discloses the use of a delayed-release pre-packaged bait container better suited for use in craypots. The Richard device is a can having a corrodible metal wall. Like the Kingston device, bait odours are not released into the water prior to the opening of the container. Also, since (like the Kingston device) the bait will tend to be retained in the container after opening, it may not be readily accessible by crays or crabs of the size desired and may present a cleaning and disposal problem.
U.S. Pat. No. 3,524,569 to Hershey and U.S. Pat. No. 4,563,832 to Drebot teach the use of a mesh-form bait bags to inhibit bait being carried outside of the trap and, in the case of Drebot, the mesh is so fine that it prevents access arthropods. However, the bait-bags are not convenient to seal, open and clean-out. They are also prone to being snagged and holed on the wires or canes of cray-pots, as well as becoming entangled with crustacea caught in the pot. Furthermore, like the bait containers of Kennedy and Sologub, those of Hershey and Drebot are not capable of effecting the timed release ofxe2x80x94or access toxe2x80x94large particles of bait.
Delayed or controlled release of bait from containers has been practised by anglers. For example, U.S. Pat. No. 5,319,875 to Brandolino discloses the use of a bait-bag which is attached to a leader from a fishing line so that a closure on the bag can be opened to release the bait by jerking the line. French patent 1,275,039 to Chopin discloses a bait container through which the fishing line is threaded so that it can rest on a sinker near the hook. The lid of the container is held closed by a piece of bread crust or paper that disintegrates in water and, after some delay, allows the container to open. This method of timed release is unreliable and quite unsuited to crayfishing. French patent 1,488,709 to Benezet discloses a multi-compartment plastic pouch in which each compartment is sealed with a cardboard panel that disintegrates in water to effect the delayed release of bait at intervals near a fishing line. However, only pre-packaged dry bait can be used (otherwise the cardboard will disintegrate before the pouch is deployed) and such bait is not suitable for crayfish.
It is the general object of the present invention to provide delayed-release bait canisters or containers suitable for use with crustacean traps that do not have one or more of the disadvantages of the prior art devices mentioned above Another general objective is to provide improved corrodible links that are well adapted for use with the delayed-release canisters of the invention.
The reusable bait canister of the present invention has a hollow body member of sufficient capacity to accommodate pieces of fresh bait or a significant amount of attractant pellets, and an opening in the body of sufficient size to allow ready access to the bait by the target crustacea. The opening can be made up of a series of sub-openings, if desired. A closure member is supported by the body member for movement between a closed position (where it covers the opening closely enough to prevent access to the bait by small fish and sea lice but loosely enough to permit flow of water into the body member when the canister is submerged) and an open position where the opening is uncovered sufficiently to permit access to the bait by the target crays or crabs. Spring means are provided to bias the closure member to the open position, and a corrodible link is used to secure the closure in the closed position against the bias of the spring, corrodible link being adapted to corrode and break under the bias of the spring means after a predetermined time of immersion in seawater.
The opening (or series of sub-openings) can be formed in a cylindrical portion of the body so that an arcuate closure can slide circumferentially on the body to cover and uncover the opening. In that event, it is convenient to form the spring means from elastic cord secured between the body and the closure in such a way that it lies over the closure and serves to both bias the closure open and to hold it against the body. After loading the canister with bait, the closure is moved to the closed position, stretching the cord, and can be held there by fitting the corrodible link overknobs or protrusions formed on the closure and the body. A fixed time after placement in a cray pot and dropping into sea water, the link will corrode and allow the cord to open the canister. Preferably, the cord is arranged to snap the closure open against a stop so that the canister spins and all (or at least some) of the bait is discharged.
In other arrangements both the closure and the body can be tube-like, the one fitting over the other and each having openings that can be moved into or out of register to conceal the bait or to provide access to it. Again, the closure is biased to the open position but held against the bias by a corrodible link. In yet another form, the canister can be folded-up from a flat sheet so that the closure is in fact formed by the last panel to be closed, and the spring means can be formed by the resilience of the sheet material itself.
While many different corrodible links can be used, some of which are disclosed by Richard in U.S. Pat. Nos. 3,724,120 and 3,426,427, we prefer to use a loop-form link that has a springy U-shape non-sacrificial (eg, copper-plated steel) element which is held closed by a sacrificial element (eg, magnesium). Thus, in the absence of any external force, the resilience of the U-shape element will cause the sacrificial element to fracture (after a predetermined time of immersion in seawater) and result in the positive opening of the loop.